The present invention relates to a device of rotating an endless belt, a transfer device that corrects the meandering of a transfer belt, for example, and an image forming apparatus provided with such a transfer device.
Conventionally, an image forming apparatus that transfers a toner image on a recording paper sheet through a transfer belt has been proposed (see Japanese Unexamined Patent Application Publication No. 2014-10429, for example). The transfer belt is stretched over a plurality of rollers arranged side by side, performs a rotating movement with rotation of the rollers, and transfers a toner image by this rotating movement. However, if a shift occurs in parallelism among the rollers due to a change with the passage of time of the rollers, each member that rotatably supports the rollers, or the like, the transfer belt may shift accordingly, that is, may meander in the axial (thrust) direction of the rollers, which may thus cause breakage of the transfer belt or deterioration of image quality. Japanese Unexamined Patent Application Publication No. 2014-10429 discloses a meandering correction technique for returning the meandering transfer belt to the original position. In other words, a meandering correction technique includes: a belt butt portion that is provided in the end portion in the axial direction of a roller and moves in the axial direction in response to the press of the side end of a meandering transfer belt, a shaft displacement portion that has an inclined surface and moves in the axial direction according to the movement of the belt butt portion, a shaft guide portion that is fixedly arranged radially outwardly as opposed to the inclined surface, and a configuration in which the shaft of the roller is inclined in the opposite direction by the reaction force received from the contact of the inclined surface of the shaft displacement portion and the shaft guide portion. According to this configuration, when the transfer belt meanders, the inclined surface changes a position of contact with the shaft guide portion, that is, the shaft of the roller is inclined, and, as a result, the meandering is corrected in response to the force with which the transfer belt returns in a direction opposite to the meandering direction.
However, the meandering correction technique disclosed in Japanese Unexamined Patent Application Publication No. 2014-10429 has the following problems. A description is given below using FIG. 6B that simply illustrates a configuration disclosed in Japanese Unexamined Patent Application Publication No. 2014-10429. On the assumption that the meandering to the left has occurred in a transfer belt 202 that rotates by rotation of a roller 201, a shaft displacement portion 203 moves to the left, a inclined surface 204 contacts a shaft guide portion 205, and the roller 201 inclines the shaft downward in the radial direction in response to the reaction force. Therefore, a position in which the shaft guide portion 205 and the inclined surface 204 contact is displaced in the radial direction of the shaft of the roller 201. For example, in the state in which a meandering quantity is small, as illustrated in FIG. 6B, a reaction force F1 occurs in a position P1 near the shaft of the roller 201, and the roller 201 receives a load in the direction of the reaction force F1. On the other hand, in the state in which the meandering quantity is large, although not illustrated in FIG. 6B, the shaft of the roller 201 is, in practice, made to be inclined more downward, accordingly, a reaction force F2 occurs in a position P2 farther away from the shaft of the roller 201, and the roller 201 receives a load in the direction of the reaction force F2. In this manner, since the roller 201 is different in the direction that receives a load according to the magnitude of the meandering quantity, smooth rotation may be damaged under a meandering state.
In view of the problems described above, various preferred embodiments of the present invention are directed to provide a belt rotating device, a transfer device, and an image forming apparatus that stabilize the rotating operation of a meandering correction roller by keeping the direction of a load constant, the load being applied to the meandering correction roller when the rotating shaft is inclined regardless of the magnitude of the meandering quantity of an endless belt.